1. Field of the Invention
The present invention relates to a method for determining membership in a database. More specifically, the present invention relates to the use of parameterized bloom filters in order to determine membership in database, such as a key invalidity database, to determine key validity.
2. Background Information
The use of credit cards, debit cards, or other types of non-cash payment methods for a transaction requires a determination of the validity of the payment means prior to the completion of the transaction. Current methods of determining validity of such payment methods includes a client/server system such as 100 shown in FIG. 1. In one prior art method, a payment method, such as a credit card 112, is used for inputting a key 114 into a client 110. Because the list of revoked credit card numbers or "keys" 114 is very large, the client 110 performs a query 116 of key validity, for example, to a server 120. Server 120 has access to a very large invalidity database 121 which contains a list of all of the invalid keys. Thus, client 110 makes a query 116 to server 120 whether the key 114 is in the database 121. The database could contain all keys, valid and invalid, and mark which keys are invalid. For simplicity, it is assumed that only invalid keys will be found when the database is querred.
Responsive thereto, server 120 performs a lookup in an invalidity database 121 to determine the presence of the key. If the key is present in the database, then it is invalid. Server 120 then either provides a valid or invalid signal to client 110 indicating whether the key is a member of the invalidity database 121 or not. If a valid signal is returned (indicating the key is not in invalidity database 121) client 110 completes the transaction.
One shortcoming of some prior art database membership applications, such as those used in the credit card verification application discussed above, is that membership in the database is determined based upon of a request from a client and a corresponding response from a server. That is, for every transaction, a communication link must be established and a database lookup must be performed. Because keys, such as credit cards, have large numbers of possible values, and correspondingly large numbers of possible invalid keys, the server 120 is capable of communicating with large numbers of clients and can service large numbers of requests.
In order to respond to all the possible requests which may occur, especially at high traffic intervals, server 120 requires a large number of communication channels, and typically should be able to service a large number of search requests in invalidity database 121 efficiently. This requires a high performance server, which may increase costs dramatically, according to the implementation.
Thus, the prior art has suffered from the shortcoming that very expensive mechanisms for verifying the validity of keys, and correspondingly large amount of communication bandwidth must be provided in order for such a key validity determination system to be fully practicable. Such a capacity stretches resources both in terms of communication resources, computational resources, and the corresponding cost of providing such resources.
Thus, a need exists for a method and apparatus which can determine membership in a database, such as an invalidity database, but yet, minimizes computational, communication, and cost resources.